Turk J Agric For
29 (2005) 305-313
© TÜB‹TAK
Evaluation of Thermal Treatability of Caucasian Fir
(Abies nordmanniana (Link.) Spach.) Treated with Heated TanalithC of CCA above and below the Fibre Saturation Point
‹lker USTA
Hacettepe University, Wood Products Industrial Engineering, 06532 Beytepe, Ankara - TURKEY
Received: 09.08.2004
Abstract: Caucasian fir (Abies nordmanniana (Link.) Spach.) was treated using the full-cell process with heated tanalith-C at elevated
temperatures from 5 to 70 ºC above and below the fibre saturation point (FSP: 32.1%) (in 40% and 20% moisture content (MC)
levels). Thermal treatability was determined on the basis of preservative uptake (the percentage of void volume filled, VVF%) in
transverse flow (a combination of tangential and radial directions) and triplex flow (based on all 3 flow directions). To characterise
the treatability, analysis of the coefficient of transverse thermal conductivity was also performed above and below the FSP. Thermal
conductivity (Tc) increased markedly with increasing temperature at either MC level. Tc was found to be relatively high at 40% MC
due to the contribution of free water in the lumens. However, VVF% did not follow the evolution of the temperature in both flow
directions at either MC level. The VVF% variation seemed to depend on the FSP, e.g., it showed almost a parabolic trend in 20%
MC, and reached the highest values in either direction at around 30 ºC.
Key Words: Caucasian fir, Thermal treatment, FSP, Elevated temperatures, Thermal conductivity
Is›t›lm›fl Tanalith-C (CCA) ile Lif Doygunlu¤u Noktas› Üzerinde ve Alt›nda Emprenye Edilen
Do¤u Karadeniz Göknar›n›n Is› Destekli Korunabilirlik Özelli¤inin Belirlenmesi
Özet: Do¤u Karadeniz göknar› (Abies nordmanniana (Link.) Spach.), 5 ºC`den 70 ºC`ye kadar de¤iflen s›cakl›klarda ›s›t›lm›fl tanalithC kullan›larak -dolu hücre yöntemine göre- lif doygunlu¤u noktas› (LDN: %32.1) üzerinde ve alt›nda (%40 ve %20 rutubet
miktar›nda) emprenye edildi. Is› destekli korunabilirlik özelli¤i, koruyucu s›v› içerilme miktar›n›n (KS‹%, a¤aç malzeme hücre
boflluklar›n›n koruyucu s›v›yla içerilmesi yüzdesi) belirlenmesiyle -te¤et ve radyal ayr›m› olmaks›z›n- liflere dik yönde ve tüm ak›fl
yönlerinin aç›k oldu¤u tripleks yönde niceliksel olarak tan›mland›. Bu özelli¤in nitelenmesi aç›s›ndan, liflere dik yöndeki ›s› iletme
katsay›s› da ayr›ca belirlendi. Is› iletme özelli¤i (I‹Ö) sonuçlar›, -LDN üzerinde ve alt›nda- s›cakl›¤›n artmas›na ba¤l› olarak I‹Ö`nin
göreceli bir flekilde artt›¤›n› gösterdi. Özellikle, hücre bofllu¤undaki serbest su miktar›n›n fazla oldu¤u %40 rutubet miktar›ndaki ›s›
iletme de¤erleri, %20 rutubet miktar›na göre, daha yüksek bulundu. Emprenye sonuçlar› ise, LDN üzerinde ve alt›nda -hem liflere
dik hem de tripleks yönde- sürekli olarak artan ›s› de¤iflimine ba¤l› olarak KS‹% de¤erlerinin do¤rusal bir flekilde artmad›¤›n›
gösterdi. Bununla birlikte, KS‹% de¤ifliminin, LDN etkisinde kald›¤› görüldü. Örne¤in, %20 rutubet miktar›ndaki KS‹% de¤iflimi, her
iki ak›fl yönünde de parabolik bir görünümde -daha düzenli bir nicelikte- gerçekleflirken, en yüksek de¤erlerine 30 ºC seviyesinde
ulaflt›.
Anahtar Sözcükler: Do¤u Karadeniz göknar›, Termik koruma, LDN, S›cakl›k art›r›m›, Is› iletme
Introduction
In recent years, much attention has been paid to the
protection of the environment. Many researchers in the
field of wood preservation have studied novel
preservation techniques; these have no or less impact on
the environment. Thermal treatment technology is one of
these.
It has long been known that the different intrinsic
wood properties (such as durability, sorption behaviour,
shrinkage and swelling behaviour, and strength
properties) are changed by thermal treatment at elevated
temperatures (Stamm, 1964; Burmester, 1973;
Giebeler, 1983). The level of change very much depends
on wood species and the process conditions, in which the
* Correspondence to: [email protected]
305
Evaluation of Thermal Treatability of Caucasian Fir (Abies nordmanniana (Link.) Spach.)
Treated with Heated Tanalith-C of CCA above and below the Fibre Saturation Point
temperature and the absence of oxygen play a
predominant role.
However, only recently in Europe have attempts been
made to develop industrially applicable technology to
thermally modify wood. Developments took place in the
Netherlands (Ruyter, 1989; Boonstra et al., 1998;
Tjeerdsma et al., 1998; Militz and Tjeerdsma, 2000),
France (Dirol et al., 1993; Vernois, 2000), Germany
(Rapp and Sailer, 2000; Rapp et al., 2000); and Finland
(Viitanen et al., 1994; Jämsä and Viitaniemi, 1998;
Syrjänen et al., 2000). The total production capacity of
heat-treated wood in 2001 was estimated at
approximately 165,000 m3, and was planned by the
3
industry to increase to some 265,000 m in 2003 (Militz,
2002).
Langrish and Walker (1993) stated that knowledge of
the thermal properties (such as the specific heat, the
thermal conductivity, and the thermal diffusivity) is not
only of importance when considering the insulating and
fire resistant properties of wood. It is also needed to
determine the steaming time for peeler logs and the
warm-up time for timber prior to kiln drying.
Furthermore, it is a necessity in preservative treatment,
especially for thermal treatment processes.
Thermal conductivity is expressed by the coefficient of
thermal conductivity (k). This is a measure of the quantity
of heat in calories that will flow during a unit of time (s)
through a body 1-cm thick with a surface area of 1 cm2,
when a difference of 1 ºC is maintained between the 2
surfaces, i.e. k is measured in (kcal m / h ºC)* (Kollmann
and Cote, 1968).
In general, the thermal conductivity of wood is low
because its structure is porous. Dry wood is one of the
poorest conductors of heat due in part to the low
conductivity of the actual cell wall materials, and in part
to the cellular nature of wood, which in its dry state
contains within the cell cavities a large volume of air –one
of the poorest conductors known (Desch and Dinwoodie,
1996). When examining the heat flow in slender pieces of
timber or round wood, the longitudinal heat flow can be
neglected even though the thermal conductivity in the
axial (longitudinal) direction is about twice the
conductivity in the transverse (tangential, radial) direction
(Siau, 1984). Important differences do not exist between
the radial and tangential directions (Ratcliffe, 1964a,
1964b, 1964c). Knigge and Schulz (1966) determined
the coefficients of thermal conductivity of different
woods at 20 ºC for 3 flow directions (in kcal m / h ºC) as
follows: 0.191–0.284 (axial), 0.104–0.151 (radial), and
0.090–0.140 (tangential).
Thermal conductivity (Tc) is influenced by various
factors, such as wood structure, density, moisture,
temperature, extractives, and defects (checks, knots,
cross grain) (Steinhagen, 1977). Sova et al. (1970)
stated that Tc increases proportionally with wood
density, moisture content (MC), and temperature.
According to Kollmann (1951), when moisture is
increased or reduced below the fibre saturation point
(FSP) by 1%, Tc is increased or reduced from 0.7% to
1.18%. However, above the FSP, the increase or
reduction is somewhat higher, and in general wood with
an MC higher than 40% has an approximately 1/3 higher
conductivity than dry wood. Furthermore, Tc is affected
by temperature. Kanter (1957) determined the k (kcal m
/ h ºC) for birch at temperatures between 20 and 80 ºC
at different MCs, and found variations from 0.17 to 0.21
at 20% MC and from 0.22 to 0.27 at 40% MC.
Little is known about the relationships between
thermal conductivity and transverse permeability, but the
thermal treatability of Caucasian fir –a refractory
softwood species– deserves further investigation.
It may be natural to assume that the preservatives
that produce a sediment (i.e. water bornes) when heated
would not be suitable for preservative treatment, because
when wood is placed in a hot preservative, moisture
evaporates and the air contained in the cell cavities
expands (Hunt and Garratt, 1967). On the other hand,
heating the water borne solutions may be more useful to
improve fluid absorption for the treatment of refractory
species when the full-cell preservative treatment is
operated by heated preservative chemicals (e.g., tanalithC of CCA). The objective of the present study, therefore,
was to clarify the role of the solution’s temperature on
the permeability of Caucasian fir in both transverse and
triplex directions at elevated temperatures ranging from
5 to 70 ºC and at MC levels above and below the FSP.
* In the English system, thermal conductivity (k) is measured as the quantity of heat in British thermal units (Btu) that will flow in 1 h through a
body 1-in thick and 1 ft2 when a difference if 1 ºF is maintained between the 2 surfaces. 1 Btu in / h ft2 ºF = 0.12404 kcal m / h ºC
306
‹. USTA
for Abies species (Pratt, 1974). Thereafter, T&R samples
were double sealed with ABS solvent cement (polymer
dissolved in methyl ethyl ketone, Durapipe).
Materials and Methods
Samples were collected from the segments of logs
used in a previous study (Usta, 2004), and prepared in
equilateral triangle cross-sections (Figure 1). Long (in 25
mm length for 240 samples) and short samples were
produced (10 mm for 60). As the physical properties of
Caucasian fir, such as the FSP (32.1%) and the
volumetric shrinkage value (βv: 11.8%), had been
determined in our preliminary report (Usta, 2004), the
short samples were used for the determination of ovendry density and the initial MC by an oven-drying process.
Data assembly and experimental processing were
conducted according to the “novel guide” (Usta and Hale,
2004). A flow chart was also designed for the
determination of thermal conductivity according to the
literature (MacLean, 1941; FPL, 1952; Deliinski, 1977;
Tsoumis, 1991) (Figure 2). To observe the effect of
temperature on the coefficient of thermal conductivity (k)
of Caucasian fir, thermal conductivity at 0 ºC (k0) was
initially determined. Since k0 is mainly influenced by
changes in MC and nominal density (R, based on oven-dry
weight and volume at the current MC), R was determined
by the following relationship: R = (βv / FSP) using data
previously reported by Usta (2004).
The levels of MC were 40% and 20% due to the FSP.
The long samples were marked for triplex flow and T&R
(transverse flow, a combination of tangential and radial
directions), and dried sequentially using the schedule K in
accordance with the recommended kiln-drying schedule
X
x2
t
3
4
5
d TR
triplex, d, T&R (mm) in equilateral triangle cross-section
25
D
10
25
E
rays
25
triplex
T&R
d
F
C
TL
B
G
A
H
s
acheid
axial tr
S
TS
(in gro
ou wth
ter ri
sap ngs
wo
od
)
S
RL
Xx
2
1.3 m
120 cm
X
x1
40 cm (each)
1
triplex flow (all faces open)
T&R (transverse flow: combination of tangential and radial flow)
for T&R: TS is sealed but both TLS and RLS are unsealed
each triplex, T&R for kiln drying process and treatment experiment
d (determinative) sample for either of triplex and T&R
each d for oven drying process and density determination
Figure 1. A diagram showing the collection and preparation of the experimental samples in equilateral triangle cross-section for determination of
thermal treatability of Caucasian fir (dimensions not to scale).
307
Evaluation of Thermal Treatability of Caucasian Fir (Abies nordmanniana (Link.) Spach.)
Treated with Heated Tanalith-C of CCA above and below the Fibre Saturation Point
oven drying process
m x (g)
(103 ± 2 °C)
triplex
to calculate
thermal conductivity (k)
k)
iMC (%)
((mx - mod) / mod ) x 100
m od (g)
m x (g)
V od (cm 3 )
((h 2 x L) / 2)
mx / ((iMC / 100) + 1)
kiln drying process
D 0 (g cm -3)
D MC (g cm -3)
R (g cm -3)
MC ≤ 25%
D 0 (1 + (MC / 100)) / 1 + (0.84 x D 0 (MC / 100))
k 0 (kcal m / h °C )
MC < 40%
(R (1.39 + (0.028 x MC))) + 0.165
sealing
(schedule)
(mod / Vod)
((βv / FSP)
m d (g)
edw (g)
preliminary data from Usta (2004)
FSP (%), Volumetric shrinkage (βv, %)
T&R
d
MC > 25%
D 0 (1 + (MC / 100)) / 1 + (D 0 (FSP / 100))
MC ≥ 40%
(R (1.39 + (0.038 x MC))) + 0.165
mk (g)
m s (g)
V d (cm 3)
((h 2
x L) / 2)
treatment process
MC (%)
(full-cell process)
((mk / edw) - 1) x 100
P (%)
(1 - (D MC / 1.5)) x 100
m t (g)
NDS (kg m -3)
blk. vol. (cm 3)
((DSR / Vd) x 1000)
(P / 100)
coefficient b
uptake (g cm -3)
MC / (1 – (270 x (D 0 / 1.5)))
(FU / Vd)
k (kcal m / h °CC )
k0 x (1 + (coefficient b x t))
VVF (%)
(uptake / blk. vol.) x 100
DSR (g)
(FU x (S / 100))
FU (g)
(mt - ms)
(mt - md)
FR (g / g)
(FU / md)
Figure 2. A schematic representation of data assembly and the experimental processing. Citations of abbreviations and definitions used in this guide
were shown sequentially on the base of the process. FSP (%), fibre saturation point; R (g cm-3), nominal density based on oven-dry weight
and volume at the current moisture content; k0 (kcal m / h ºC), coefficient of thermal conductivity at 0 ºC; coefficient b, a proportionality
coefficient related to the effect of density and moisture content (MC); k (kcal m / h ºC), coefficient of thermal conductivity by the effect of
temperature; t (ºC), temperature; mx (g), the green mass; Vod (cm3), block volume after oven drying; mod (g), oven-dried mass; D0 (g cm3
), oven-dry wood density; DMC (g cm-3), wood density at respective moisture contents (MC ≤ 25%, equal to-and/or-below 25 percent
moisture content; MC > 25%, above 25 percent moisture content); P (%), porosity; blk. vol. (cm3), the amount of space available in a
given block volume; iMC (%), initial moisture content; edw (g), estimated dry weight after kiln drying; mk (g), mass of the sample for
control the current MC at regular intervals; MC (%), current moisture content at regular intervals during drying; Vd (cm3), block volume
after kiln drying; md (g), mass after kiln drying (before treatment); ms (g), sealed mass; mt (g), mass after treatment process; FU (g),
fluid uptake (the gross preservative solution absorption), FR (g/g), fluid retention (preservative retention on a whole-block basis); NDS (kg
m-3), net dry salt absorbed after impregnation; DSR (g), dry salt retention on the base of its strength; S (%), strength of solution; uptake
(g cm-3), dry salt loadings based on weight per volume; VVF (%), void volume filled by preservative solution.
Thermal treatment process: Recent efforts
concerning the thermal treatment of wood have led to the
development of several new processes introduced on the
European market during the last few years (e.g., Platoprocess (PLATO BV, the Netherlands), Ratification
Process (NOW New Option Wood, France), Bois perdure
(BCI-MBS, France), OHT-process (Oil-Heat Treatment,
Menz-Holz, Germany), and Thermo-Wood process
308
(Stora, Finnforest, Finland)). These processes have in
common the treatment of sawn wood at elevated
temperatures in the range between 160 and 260 ºC. The
main differences between the processes are to be seen in
the process conditions (process steps, oxygen or
nitrogen, steaming, wet or dry process, use of oils,
steering schedules etc.) and they have been published in
several patents (EP0018446, 1982; EP892031709,
‹. USTA
1989; EP0612595, 1994; EP0623433, 1994;
EP0622163, 1994; EP0759137, 1995; US5678324,
1997).
In comparison with the existing industrial processes
overviewed, our thermal treatment process has been
designed on a pilot scale with heating as the solution to
lower temperatures. The treatment operation was
carried out using a model pressure treatment plant
according to BS 4072 (1987 part 2). The samples were
treated with a 2% concentration of heated tanalith-C at
14 elevated temperatures from 5 to 70 °C, in addition to
a non-heated (control) treatment, by a mild full-cell
treatment schedule of 15 minutes vacuum (–0.84 bar)
followed by pressure (1 bar) for 5 min. No final vacuum
was used. A non-heated (control) treatment was also
performed for comparisons. Each sample was weighed
before and after a 5 min drip period following treatment
to obtain the theoretically maximum possible solution
uptake and dry salt absorption based on void volume (%)
(McQuire, 1975).
Results and Discussion
k (Kcal m/h °C)
Thermal conductivity: The coefficient of thermal
conductivity (k) at elevated temperatures was calculated
-3
based on R (0.368 g cm ) (Figure 3). It was observed
that the coefficient of thermal conductivity at 0 ºC (k0,
2
kcal m / h ºC) was 0.109 (0.883 Btu in / h ft ºF) at 20%
2
MC and 0.153 (1.236 Btu in / h ft ºF) at 40% MC.
Furthermore, the results indicate that k is a linear
function of the temperature. When this relationship was
established for each MC separately, there was a good
2
correlation (R = 1) between temperature and k (Figure
3). Let ki,j be the thermal conductivity at temperature i
(ºC) and MC j (%). The extreme values were k5,20 = 0.110
and k5,40 = 0.157, and k70,20 = 0.130 and k70,40 = 0.211.
The ratios k5,40/k5,20 and k70,40/k70,20 thus became 1.42
and 1.62, respectively. The following relationships are
suggested: (y = 0.153 + 0.0041 x) for MC 40% and
(y = 0.109 + 0.0015 x) for MC 20%. It should be noted
that these experimental results show good agreement
with data from the literature for a refractory softwood
species (Steinhagen, 1977; Tsoumis, 1991).
Although the thermal conductivity of Caucasian fir
appeared to be fairly low at either MC level, we assume
that these values reflected intrinsic information on the
internal properties and fine structure of cell wall
constituents of this species. This characteristic renders
Caucasian fir eminently suitable for use in timber frame
house construction, indoor panelling, and wall cladding
and/or sheathing. In addition, Siau (1984) stated that the
low conductivity of wood accounts for the considerable
time interval required to bring a large-diameter pole or
bolting to a uniform, elevated temperature by the
application of heat to its external surfaces. Such
unsteady-state heating is, therefore, an important part of
wood treatment.
Treatability by heated solution: The effects of
temperature on the percentage of void volume filled
(VVF%) with heated tanalith-C at different MC levels
above and below the FSP are given in Table 1 for both
triplex and transverse (T&R) flow, and changes in VVF%
at the elevated temperatures from 5 to 70 ºC are shown
in Figure 4.
In general, the results showed that there are upward
and downward trends in VVF% at the elevated
temperatures at either MC level. All these trends indicated
the dependence of permeability (fluid flow) on MC and
partially on the temperatures. In regard to the elevated
temperatures, the trends at the dry samples (at 20% MC)
indicated a close relation to the VVF% variation pattern in
0.210
0.190
40% MC
0.170
20% MC
0.150
0.130
0.110
0.090
0
5
10
15
20
25 30 35 40
Temperature (°C)
45
50
55
60
65
70
Figure 3. Evolution of the coefficient of transverse thermal conductivity in Caucasian fir above and below
the fibre saturation point over the elevated temperature. MC: Moisture content
309
Evaluation of Thermal Treatability of Caucasian Fir (Abies nordmanniana (Link.) Spach.)
Treated with Heated Tanalith-C of CCA above and below the Fibre Saturation Point
98
triplex flow
all faces open
VVF%
81
40% MC
64
20% MC
47
30
64
VVF%
56
transverse flow
T&R
47
39
30
control 5
10
15
20
25
30 35 40 45
Temperature (°C)
50 55
60 65 70
Figure 4. Changes in the percentage of void volume filled (VVF%) with heated
preservative solution at elevated temperatures for triplex flow and transverse
flow in 40% and 20% MC (moisture content).
either flow direction. However, the trends of the wet
samples (at 40% MC) did not show a specific pattern. As
shown in Table 1, VVF% increased and reached a peak at
around 30 ºC at both MC levels in each flow direction,
after which it decreased either dramatically (at 40%) or
slowly (at 20%) to around the level of the non-heated
(control) samples.
In type 2 (pattern of transverse -T&R- flow), VVF%
at 40% MC decreased dramatically after 25 ºC and
assumed lower values in comparison with those for 20%
MC. In addition, the results of VVF% at the higher
temperatures showed a similar pattern for either of these
2 MC levels, i.e. there were steady changes after 60 ºC,
with narrow fluctuations at 40% MC.
In addition, the VVF% variation at temperatures from
5 ºC to 25 ºC in transverse flow appeared to be always
greater at 40% MC than at 20% MC, and reached the
highest value at 25 ºC. This trend was also seen in triplex
flow. According to Langrish and Walker (1993), this
outstanding performance could be technically suitable and
advantageous for thermal treatment in the artificial
drying of green wood, where the rapid conduction of heat
throughout the stack is essential.
In type 3 (pattern of triplex flow), the VVF% variation
at 20% MC showed trends similar to those observed for
transverse flow. However, there was a different trend at
40% MC. The VVF% variation at 40% MC was initially
consistent with the trends at 20% MC until 40 ºC, but
after that it apparently decreased.
It has been noted that the thermal treatability of
Caucasian fir based on the trend of VVF% variations over
the designed levels of temperature may be of 3 different
types for either MC level in each flow direction (with a
statistically significant difference at P < 0.05) (Figure 4).
In type 1 (consistent with either flow direction),
VVF% increased for temperatures increasing from 5 ºC to
25 ºC at 40% MC, and from 5 ºC to 30 ºC at 20% MC.
In the case of the highest value, VVF% was numerically
superior at 30 ºC in triplex flow, and at 35 ºC in
transverse flow.
310
It is clear from Table 1 and Figure 4 that Caucasian fir
has low thermal treatability features, especially in the
transverse direction (perpendicular to the fibre axis),
where there is high resistance to flow due to the
interruption of the path by the poorly conducting airfilled lumens. Based on the VVF% with heated tanalith-C,
it was observed that the greatest preservative uptake
occurred at around 30 ºC in both transverse and triplex
directions, and higher temperatures did not improve the
uptake most likely due to the effects of vaporisation,
particularly at higher MC (40%). This result indicates that
heating the solution causes the air in the wood to expand
and some of it is forced out. Consequently, 20% MC and
temperature around 30 ºC (not less than 25 ºC and not
‹. USTA
Table 1. Effect of temperature on the percentage of void volume filled (VVF%) with heated preservative
solution in triplex and transverse (T&R) directions at 40% and 20% moisture content.
Triplex flow
Temperature
(ºC)
Control
Transverse (T&R) flow
40%
20%
40%
20%
54.9 ± 0.16 a
59.3 ± 0.03 a
43.0 ± 0.99 a
40.1 ± 0.18 a
5
67.5 ± 1.09 b
68.0 ± 1.61 b
48.2 ± 0.24 b
41.7 ± 1.67 ab
10
74.6 ± 0.84 c
76.1 ± 0.67 c
53.3 ± 0.27 c
44.2 ± 0.85 b
15
91.3 ± 3.17 d
89.5 ± 211 d
56.5 ± 0.51 d
49.3 ± 0.28 c
20
95.2 ± 0.76 d
93.5 ± 2.09 d
59.9 ± 0.92 e
54.2 ± 0.23 dh
25
102.8 ± 0.08 e
99.3 ± 0.93 e
63.3 ± 0.30 f
57.6 ± 0.95 eg
30
103.0 ± 0.06 e
101.6 ± 0.99 e
55.5 ± 0.51 gcd
59.8 ± 1.31 ef
35
95.1 ± 0.07 d
97.1 ± 0.59 e
51.6 ± 0.58 hc
60.3 ± 0.32 f
40
93.3 ± 0.25 d
91.2 ± 1.08 d
49.8 ± 1.78 hib
59.4 ± 0.78 f
45
70.9 ± 2.40 fbc
90.4 ± 1.23 d
47.5 ± 0.51 ikb
58.4 ± 0.40 fg
50
64.4 ± 2.13 gb
83.7 ± 0.14 f
46.1 ± 0.94 k
54.4 ± 0.40 h
55
52.5 ± 2.36 a
73.4 ± 0.68 c
43.4 ± 1.46 ma
51.7 ± 0.74 i
60
47.4 ± 1.05 h
69.4 ± 0.40 b
41.9 ± 0.86 mna
48.9 ± 1.16 kc
65
46.6 ± 0.62 h
62.7 ± 3.41 ba
40.1 ± 1.05 np
48.1 ± 1.05 kc
70
46.4 ± 0.83 h
60.9 ± 1.69 a
39.9 ± 0.87 p
47.7 ± 1.73 kc
Values shown are the means with the standard deviations of 4 replicates
Means that are not significantly different at P < 0.05 level (Tukey comparison test) have the same letter
in a given column.
Control samples were treated with non-heated preservative solution
more than 35 ºC) were highlighted as reliable
specifications for heating the tanalith-C.
These experimental findings provided important clues
for the improvement of preservative uptake in Caucasian
fir, which is a refractory softwood species, treated with
heated tanalith-C. In the future, however, more detailed
studies on this species at different experimental
conditionsincluding the use of other preservative
chemicalswill be necessary to identify efficient
utilisation for the thermal treatment process.
Conclusions
This study has shown preservative uptake in
Caucasian fira refractory speciescan be improved by
heated tanalith-C (CCA) to make it more suitable for use
with a mild thermal treatment process under the
conditions of 20% MC and 30 ºC temperature. This
application may provide new industrial uses in wood
preservation. As the pipingfor transferring the heated
preservative solution to the cylinderwas designed in
this study without steaming, additional work on using
steam piping between the tank and the cylinder is now
under way. Laboratory studies will soon be performed in
order to optimise the processing parameters and to
evaluate the process economics.
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